The Effect of Pollen Limitation on Plant Reproductive Systems and the Maintenance of Sexual Polymorphisms

Maurice, Sandrine; Fleming, Theodore H.

doi:10.2307/3545674

Cited by 91 publications

(94 citation statements)

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“…Sexual diversity of this type is now reported from numerous species, raising the question of how it originates and whether it represents a stable sexual system, or is simply a transient condition associated with the evolution of dioecy, as Darwin surmised (Lloyd 1976;Charlesworth & Charlesworth 1978;Ehlers & Bataillon 2007). Theoretical investigations of the evolutionary maintenance of subdioecy indicate that coexistence of three sexes can occur as a stable polymorphism, although under restrictive conditions (Maurice & Fleming 1995;Ehlers & Bataillon 2007), or simply cannot be maintained All plants in each sample were recorded as female (grey bar), male (black bar) or non-reproductive (vegetative; white bar). Age was estimated based on annual shoot growth, since each internode represents a single year of growth.…”

Section: Sex Ratio Variation In Dioecious Plant Populationsmentioning

confidence: 99%

Ecological genetics of sex ratios in plant populations

Barrett

Yakimowski

Field

et al. 2010

Phil. Trans. R. Soc. B

120

112

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In many angiosperm species, populations are reproductively subdivided into distinct sexual morphs including females, males and hermaphrodites. Sexual polymorphism is maintained by frequencydependent selection, leading to predictable sex ratios at equilibrium. Charles Darwin devoted much of his book 'The Different Forms of Flowers on Plants of the Same Species' (1877) to investigating plant sexual polymorphisms and laid the foundation for many problems addressed today by integrating theory with empirical studies of the demography and genetics of populations. Here, we summarize our recent work on the ecological and genetic mechanisms influencing variation in sex ratios and their implications for evolutionary transitions among sexual systems. We present the results of a survey of sex ratios from 126 species from 47 angiosperm families and then address two general problems using examples from diverse angiosperm taxa: (i) the mechanisms governing biased sex ratios in dioecious species; (ii) the origins and maintenance of populations composed of females, males and hermaphrodites. Several themes are emphasized, including the importance of non-equilibrium conditions, the role of life history and demography in affecting sex ratios, the value of theory for modelling the dynamics of sex ratio variation, and the utility of genetic markers for investigating evolutionary processes in sexually polymorphic plant populations.

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Section: Sex Ratio Variation In Dioecious Plant Populationsmentioning

confidence: 99%

Ecological genetics of sex ratios in plant populations

Barrett

Yakimowski

Field

et al. 2010

Phil. Trans. R. Soc. B

120

112

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“…Under PL, a female's success is limited by mating opportunities, like male success, rather than by her capacity to produce seeds, so that the pollination environment determines the nature of selection on floral traits. As a result, PL theoretically has diverse evolutionary consequences, such as reducing the threshold inbreeding depression that allows the evolution of selfing, restricting the conditions necessary for initial stages in the evolution of heterostyly and increasing the equilibrium frequency of hermaphrodites in gynodioecious and subdioecious populations (Lloyd 1974(Lloyd , 1992Lloyd & Webb 1992;Maurice & Fleming 1995;. According to this view, selection through female function for traits that increase pollen deposition and post-pollination pollen success should vary positively with the intensity of PL, an expectation confirmed for traits involved in pollinator attraction (Ashman & Morgan 2004).…”

Section: Introductionmentioning

confidence: 99%

Floral adaptation and diversification under pollen limitation

Harder

Aizen

2010

Phil. Trans. R. Soc. B

153

151

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Pollen limitation (PL) of seed production creates unique conditions for reproductive adaptation by angiosperms, in part because, unlike under ovule or resource limitation, floral interactions with pollen vectors can contribute to variation in female success. Although the ecological and conservation consequences of PL have received considerable attention in recent times, its evolutionary implications are poorly appreciated. To identify general influences of PL on reproductive adaptation compared with those under other seed-production limits and their implications for evolution in altered environments, we derive a model that incorporates pollination and postpollination aspects of PL. Because PL always favours increased ovule fertilization, even when population dynamics are not seed limited, it should pervasively influence selection on reproductive traits. Significantly, under PL the intensity of inbreeding does not determine whether outcrossing or autonomous selfing can evolve, although it can affect which response is most likely. Because the causes of PL are multifaceted in both natural and anthropogenically altered environments, the possible outcrossing solutions are diverse and context dependent, which may contribute to the extensive variety of angiosperm reproductive characteristics. Finally, the increased adaptive options available under PL may be responsible for positive global associations between it and angiosperm diversity.

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“…To differing degrees, seed production in both females and hermaphrodites is dependent upon the availability of pollen donors (Lewis 1941;Lloyd 1974;Maurice and Fleming 1995). Because pollen flow in many plant populations is predominantly local (Levin and Kerster 1974;Handel 1983;Levin 1988), it is likely that the gender of near neighbors has a significant influence on the reproductive success of individual plants.…”

mentioning

confidence: 99%

“…Whereas females are obligate outcrossers, dependent upon hermaphrodite pollen for reproduction, hermaphrodites of most gynodioecious species are self-compatible (Charlesworth 1981). As long as transfer of self pollen requires less pollinator effort than outcrossing, females should be more vulnerable than hermaphrodites to pollen limitation (Maurice and Fleming 1995). However, if hermaphrodites have low selfing rates or high genetic load, they too are expected to be pollen limited.…”

mentioning

confidence: 99%

“…However, if hermaphrodites have low selfing rates or high genetic load, they too are expected to be pollen limited. In general, pollen limitation should reduce seed set in unisexuals compared to hermaphrodites, permitting a wider range of conditions under which hermaphrodites can be maintained (Maurice and Fleming 1995). Indeed, in the one gynodioecious and one trioecious species in which pollen limitation has been measured in both females and hermaphrodites (G. hederacea and Pachycereus pring lei), females have been shown to be more pollen limited than hermaphrodites (Widen 1992;Fleming et al 1994).…”

mentioning

confidence: 99%

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POPULATION SEX STRUCTURE AND REPRODUCTIVE FITNESS IN GYNODIOECIOUS SIDALCEA MALVIFLORA MALVIFLORA (MALVACEAE)

Graff

1999

Evolution

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Abstract.-The spatial distribution of females and hermaphrodites within gynodioecious populations is expected to exert considerable selective pressure on gender fitness through pollen limitation of seed set. If pollen flow is predominantly local, seed set in individual plants may be sensitive to the proximity of pollen donors; pollen limitation of seed set may occur if hermaphrodites are locally rare. Under such circumstances, female fitness will be negatively frequency dependent and hermaphrodite fitness will be positively frequency dependent. Given local seed dispersal, a nonrandom clumped distribution of the genders is expected in gynodioecious populations due to the heritability of gender in gynodioecious species. If gender fitness is frequency dependent, such structure should favor hermaphrodites and select against females. To test this hypothesis, I quantified the distribution of the genders in terms of nearest neighbors and neighborhood sex ratio in two populations of gynodioecious Sidalcea malvijlora malviflora. I then measured the effect of neighborhood sex ratio on open-pollinated seed set and pollen limitation in both manipulated and unmanipulated neighborhoods. Results indicate that the genders have a patchy distribution and that both genders are pollen limited and show an increase in seed set with an increase in neighborhood hermaphrodite frequency. The observed population sex structure favors hermaphrodites and disadvantages females. These results highlight the importance that population-level traits can have in determining individual fitness and the evolution of sex ratios in gynodioecious species.Key words.-Frequency-dependency, gynodioecy, pollen limitation, population structure, sex ratio, Sidalcea.Received September 30, 1998. Accepted June 8, 1999.A major issue in the evolution of plant sexual systems is how both hermaphrodite and female (male-sterile) individuals are maintained in populations of gynodioecious species. Recent modeling efforts have emphasized the role of population structure in determining sex ratios in gynodioecious populations. To date, most of these models have focused on among-population, rather than within-population structure, and on genotypic, rather than phenotypic, structure. Genotypic models address the cytonuclear inheritance of male sterility in which maternally inherited cytoplasmic genes code for male sterility, whereas nuclear genes restore male fertility (Saumitou-Laprade et al. 1994). These models suggest that the widely varying sex ratios found among gynodioecious populations are determined by metapopulation processes including mutation rates among sex-determining genes and the migration of alleles between separate populations (Frank 1989;

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The Effect of Pollen Limitation on Plant Reproductive Systems and the Maintenance of Sexual Polymorphisms

Cited by 91 publications

References 10 publications

Ecological genetics of sex ratios in plant populations

Ecological genetics of sex ratios in plant populations

Floral adaptation and diversification under pollen limitation

POPULATION SEX STRUCTURE AND REPRODUCTIVE FITNESS IN GYNODIOECIOUS SIDALCEA MALVIFLORA MALVIFLORA (MALVACEAE)

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